A closed headphone of which an ear pad is tightly put into close contact with user's ear auricle and its periphery, can highly insulate the user from ambient noise and prevent sound from leaking to the exterior. Furthermore, a closed space defined by the ear pad provides a large volume of front air chamber, which is a space in front of the baffle plate and in communication with an ear canal. The space improves the quality of reproduced sound in low to medium frequency bands.
The structure of a typical conventional headphone is explained with reference to a longitudinal sectional-view in FIG. 4. The headphone 60 includes a front air chamber 64 that is a space defined by a baffle plate 62 fixed so as to block an opening of an ear cup 61 and an ear pad 63 fixed to the baffle plate 62 and that is in communication with user's ear canal. A speaker unit 65 is fixed to the baffle plate 62 in a back air chamber opposite to the front air chamber 64. The speaker unit 65 reproduces musical sound input from a sound source (not shown) and outputs the musical sound to the front air chamber 64.
The baffle plate 62 is a disk that has a central opening and a disk flange 621 having a central opening and a cylindrical rib protruding from the baffle plate 62. The baffle plate 62 and the flange 621 have different outer diameters. The baffle plate 62, the flange 621, and the cylindrical rib define a groove 622 over the entire circumference.
The ear pad 63 is composed of a substantially toroidal cushioning material covered with a skin, part of the skin being provided with a flap 631 of an elastic material. The ear pad 63 is engaged with the baffle plate 62 such that the flap 631 covers the flange 621.
The headphone 60 includes a headband (not shown) composed of a resilient material and attached to the outside (right in FIG. 4) of the ear cup 61. The other end of the headband is attached to another headphone having the same structure with headphone 60. The pair of (left and right) headphones constitutes a headphone system.
When a user wears the headphone 60 having such a structure in a determined posture, the ear pad 63 comes into close contact with the skin of his/her ear auricle and/or its periphery. This lateral pressure compresses the ear pad 63. The compression of the ear pad 63 enhances the close contact and thus comfort for the user to wear.
Compression of the ear pad 63, however, results in a reduction in volume of the front air chamber 64, which has been defined by the thickness of the ear pad 63. Since the volume of the front air chamber 64 influences the quality of reproduced sound in low to medium frequency bands as described above, the reduction in the volume adversely affects the quality of sound in low to medium frequency bands of the headphone 60.
In order to prevent the degradation of the quality of sound caused by such a reduction in volume of the front air chamber 64, the volume of the front air chamber 64 should be preliminarily increased. This requires a larger ear pad 63. The larger ear pad 63, however, requires an increase in size of the baffle plate 62 in proportion to the size of the ear pad 63, which also leads to an increase in size of the ear cup 61, resulting in an increase in size of the headphone 60 as a whole. Since an excessively large headphone is inconvenient for users, an increase in size of the ear pad 63 needs to be limited.
A known headphone is equipped with a substantial volume of a front air chamber isolated from a back air chamber without increase in size of an ear pad and has improved performance such as an enhanced sound insulation achieved by high passive transmission loss of external noise (for example, refer to Japanese Unexamined Patent Application Publication No. 2009-17176).